Update main.yml

Author: Swimburger

.github/workflows/main.yml

@@ -26,6 +26,10 @@ jobs:
  # changes the base-tag in index.html from '/' to 'BlazorGitHubPagesDemo' to match GitHub Pages repository subdirectory
  - name: Change base-tag in index.html from / to BlazorGitHubPagesDemo
  run: sed -i 's/<base href="\/" \/>/<base href="\/BlazorGitHubPagesDemo\/" \/>/g' release/wwwroot/index.html
+ 
+ # copy index.html to 404.html to serve the same file when a file is not found
+ - name: copy index.html to 404.html
+ run: release/wwwroot/index.html release/wwwroot/404.html
 
  # add .nojekyll file to tell GitHub pages to not treat this as a Jekyll project. (Allow files and folders starting with an underscore)
  - name: Add .nojekyll file